Until now, production apparatuses and production methods wherein a group-III nitride semiconductor layer that includes nitride compound semiconductor crystals, etc. is formed by a sputtering method such as a reactive sputtering method have been studied. In such a conventional reactive sputtering method, a target containing group-III elements such as Ga or Al, which is disposed inside the sputtering apparatus, is sputtered while plasma of a reactive gas including nitrogen elements (such as a nitrogen gas) is generated whereby the group-III elements are reacted with the reactive gas to form a group-III nitride semiconductor layer.
For example, a method wherein a GaN layer is formed on the (100) plane of Si and the (0001) plane of sapphire (Al2O3) by a radio frequency magnetron sputtering method using N2 gas is mentioned (for example, see Yukiko Ushiku et al.: “21st seiki rengo symposium ronbunshyu”, vol. 2, p 295, 2003).